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Liquid Gypsum: micronised calcium sulphate for clay soil and lawns
19.55% Calcium 15.31% Sulphur 5 Micron Average Particle Contains Fulvic Acid Naturally Mined Thick Mineral Suspension
Liquid gypsum earns its place by doing two jobs at once: feeding calcium and sulphur, and helping dispersive clay drain. One product does four jobs that usually need four: it is a calcium fertiliser for tomatoes, peppers and apples prone to blossom end rot and bitter pit; a liquid gypsum clay breaker that helps dispersive clay soils drain without surface disturbance; a lawn feed that supplies calcium and sulphur to turf and reaches the clay beneath it without digging; and a general source of plant-available calcium and sulphur for any fruiting crop, leafy vegetable, perennial border or container plant. One of the few liquid products that can reach clay under a lawn or border without digging it in.
This is a thick, creamy mineral suspension, not a thin liquid, not a manufactured solution. It is made by wet-milling natural gypsum (calcium sulphate) down to an average particle size of just 5 microns and suspending those micronised mineral particles in water with fulvic acid. When you open the bottle, the product is dense, opaque, and settles on standing, because it is real, physical mineral held in suspension. Milling the mineral fine is what makes it dissolve quickly. Bolan and colleagues measured powdered gypsum dissolving two to ten times faster than pelletised discs, and three to eight times faster again in the presence of soil. We do not put a clock on it, because how fast it reaches your soil depends on your soil and your rainfall. It does not change how much calcium a dose contains.
Two ingredients: mined calcium sulphate, suspended in fulvic acid. No synthetic dispersants. The mineral is suspended in fulvic acid, which is the carrier. Mined mineral, not an industrial by-product. Not all liquid gypsum is the same: for the difference between a mined mineral suspension and a synthetic manufactured one, see the Mined vs Synthetic tab.
19.55%Calcium (Ca)
15.31%Sulphur (S)
5μmAverage particle
No changeTo soil pH in the short term
What is liquid gypsum used for in the UK garden?
- Blossom end rot in tomatoes, peppers, courgettes & aubergines: blossom end rot is mainly a calcium transport and water-relations problem rather than a shortage of calcium in the soil, so consistent watering matters more than any calcium product. Gypsum is worth using where a soil test shows calcium is genuinely low.
- Liquid gypsum for lawns: calcium and sulphur feed, and clay conditioning under turf: calcium is a structural component of grass cell walls; sulphur supports deeper green colour and protein synthesis; and the calcium reaches the clay beneath the turf without digging or lifting it
- Liquid gypsum for clay soil: a clay breaker for clay that disperses: dissolving gypsum puts calcium into the surface water and holds the concentration above the line at which clay stops holding together, and deeper down calcium also swaps onto the clay in place of sodium. It works without altering soil pH
- Calcium fertiliser for fruiting crops and container plants: supplies plant-available calcium to any high-demand fruiting crop (apples, pears, strawberries, cucumbers, courgettes), perennial border, rose bed or container without raising soil pH the way lime does. The everyday calcium source for gardeners on already-neutral soils
- Bitter pit in apples & pears: bitter pit is associated with low calcium in the fruit rather than in the soil, and the evidence for soil-applied calcium is thin; orchard practice relies on fruit-directed sprays
- Tip-burn in leafy crops: lettuce, cabbage, kale. Tip-burn is mainly a calcium delivery failure in fast-growing leafy crops rather than a shortage of calcium in the soil, so consistent watering matters more than any calcium product
- Sulphur supply: gypsum supplies sulphur as sulphate. Fleuridor and colleagues measured gypsum "consistently increased S concentrations (P < .1) in soil and crop tissues as soon as 5 mo after each application" across fourteen Ohio dairy fields
- Cell wall construction in fruiting crops: calcium is a structural component of every new plant cell wall; fruiting crops have extremely high calcium demands during fruit set and fill
- Foliar calcium spray for rapid correction: the micronised suspension can be applied as a foliar spray for rapid calcium delivery directly through the leaf surface
Calcium fertiliser comparison: liquid gypsum vs lime, which one is right for your soil?
Liquid Gypsum (Calcium Sulphate)
- Delivers calcium without changing soil pH in the short term, suitable for neutral and alkaline soils
- Supplies sulphate-sulphur at the same time
- Dissolving gypsum raises the salt concentration of the surface water, which suppresses dispersion; calcium also swaps onto the clay in place of sodium
- Micronised to a 5 micron average particle, which is what makes it dissolve quickly
- Suspended in fulvic acid, which is the carrier
- Mined mineral, not an industrial by-product
Agricultural Lime (Calcium Carbonate)
- Significantly raises soil pH, useful only where acidity needs correcting
- Does not supply sulphur
- Can raise pH above optimal range on already-neutral soils
- The correct choice when both acidity and calcium deficiency need addressing
Important: what liquid gypsum cannot fix
Liquid gypsum acts on clay that disperses in water, where the plates come apart, block the pores beneath and seal the surface. It does not fix drainage problems caused by mechanical compaction (foot traffic, machinery, building work) or by a lack of physical drainage (high water table, impermeable subsoil pan, missing land drains, poor site grading). If water sits on your soil because it has nowhere to drain to, no liquid product will resolve that. You need physical drainage infrastructure. See the How to Use tab for diagnostic tests.
Mined vs synthetic liquid gypsum: what is actually in the bottle?
Not all liquid gypsum is the same. The words "liquid gypsum" on a label tell you the product contains calcium sulphate in liquid form, but they tell you nothing about where that calcium sulphate came from, how it was processed, or what else is in the bottle. There are two fundamentally different types of liquid gypsum on the market, and the distinction matters.
Two types of liquid gypsum: what is actually in the bottle
Mined Mineral Gypsum (This Product)
- Gypsum source: Naturally mined mineral calcium sulphate, quarried from geological deposits of natural gypsum rock
- How it is made: The natural gypsum is wet-milled (micronised) to an average particle size of 5 microns and suspended in water with fulvic acid. No chemical processing, no synthetic additives
- Physical form: Thick, creamy, opaque suspension that settles on standing, because it contains real mineral particles held in liquid
- Additives: None. No synthetic surfactants, dispersants or stabilisers
- Provenance: Mined mineral, not an industrial by-product
- Ingredients: Two ingredients: mined calcium sulphate, suspended in fulvic acid. No synthetic dispersants
Synthetic Manufactured Liquid Gypsum
- Gypsum source: Industrial byproduct calcium sulphate, typically from flue gas desulphurisation (FGD gypsum from coal power stations) or phosphoric acid manufacture (phosphogypsum from fertiliser factories)
- How it is made: The industrial byproduct gypsum is dissolved or dispersed using synthetic surfactants, chemical dispersants, and stabilisers to create a pourable liquid product
- Physical form: Often thinner and more uniform than mineral suspensions. Synthetic dispersants prevent the natural settling that occurs in genuine micronised mineral products
- Additives: Synthetic surfactants, chemical dispersants, stabilisers, and sometimes polyacrylamide or other manufactured polymers to maintain suspension stability
- Provenance: Recovered from an industrial process rather than mined
Head-to-head comparison
| Feature | Mined Mineral Gypsum (This Product) | Synthetic Liquid Gypsum |
|---|---|---|
| Gypsum source | Naturally mined mineral gypsum | Industrial byproduct (FGD or phosphogypsum) |
| Processing | Mechanical micronisation only, no chemical processing | Chemical dissolution with synthetic dispersants and surfactants |
| Particle size | 5 microns average, extremely high surface area for fast dissolution | Variable, often coarser or chemically dissolved rather than micronised |
| Fulvic acid | Included as the carrier | Not included |
| Synthetic additives | None | Surfactants, dispersants, stabilisers, sometimes polyacrylamide |
| Naturally mined | Yes, naturally mined | No |
| Calcium & sulphur | 19.55% Ca, 15.31% S | Variable, depends on manufacturing process and dilution |
| Residual benefit | Mineral particles continue dissolving after application | Often pre-dissolved before it reaches the soil |
Where synthetic liquid gypsum comes from
Most manufactured liquid gypsum is made from industrial byproduct gypsum, calcium sulphate produced as a waste product from other industrial processes, not mined from the ground. The two most common sources are:
01
FGD Gypsum (Flue Gas Desulphurisation)
Produced in coal-fired power stations when sulphur dioxide is scrubbed from the exhaust gas using limestone. The resulting calcium sulphate is recovered from an industrial process rather than mined. Kost and colleagues compared trace elements in soil, crop tissue and water under mined and FGD gypsum and reported that "most R values varied only slightly from 1.00".
02
Phosphogypsum
Produced during the manufacture of phosphoric acid from phosphate rock. It is cheaper than mined gypsum, which is why it is used in manufactured liquid gypsum products where cost is the primary consideration. It is worth being straight about this: much of the field evidence for gypsum on clay, including Miller 1987 and Ben-Hur 1992, was run on phosphogypsum, so we make no efficacy claim against it.
Why the additives matter
Synthetic liquid gypsum requires chemical dispersants and surfactants to stay in suspension and pour smoothly. These are industrial chemicals designed to prevent particle settling. They are not there for the benefit of your soil or plants. In a mined mineral suspension, the product settles naturally because it is real mineral in water with no synthetic stabilisers. You shake it before use, and that is the trade-off. The fulvic acid in this product is not a dispersant. The mineral is suspended in fulvic acid, which is the carrier.
How to tell what you are buying
Check the label for the gypsum source. If it does not state "natural gypsum" or "mined gypsum", the calcium sulphate is likely an industrial byproduct. If the ingredient list includes surfactants, dispersants, polyacrylamide, or other synthetic additives, the product is manufactured rather than a mined mineral suspension. If the liquid does not settle or separate on standing, it almost certainly contains synthetic dispersants. A genuine mineral suspension will always settle. Ours is quarried from natural rock rather than recovered as an industrial by-product, and the only additive is fulvic acid.
Both deliver calcium sulphate, so why does the source matter?
The calcium sulphate itself is the same molecule regardless of source. What differs is provenance and what else is in the bottle. Ours is mined mineral rather than recovered as an industrial by-product, and the only other ingredient is the fulvic acid it is suspended in. We do not claim a purity advantage we cannot show: Kost and colleagues measured trace elements in soil, crop tissue and vadose water under both mined and FGD gypsum and found most values varied only slightly from 1.00. Anything we say about contaminants would need a certificate of analysis behind it, and we do not publish one yet.
How to apply liquid gypsum: preparation, application rates & UK garden guide
Shake well before every use
This is a thick mineral suspension, not a clear solution. The micronised gypsum particles settle on standing. Shake or stir vigorously for at least 30 seconds before measuring. If the bottle has been sitting for an extended period, invert and shake several times before use. The thick, creamy consistency when shaken is normal: it is what genuine micronised mineral looks like in liquid form. Do not store in a pre-diluted form. Always dilute fresh for each application.
Application rates
On how often to apply
We attach a frequency to one rate only, lawn clay conditioning at 15 ml/L fortnightly for three months. For everything else, repeat on the symptom rather than the diary: water standing after rain, and a thin crust you can peel back with a knife.
Root drench: general maintenance
Standard rate for all plants during the growing season. Apply around the root zone, not over the crown. Water in well after application. Compatible with all Dr Forest fertilisers.
Root drench: active deficiency or high demand
The corrective rate, for use where a soil test shows calcium is genuinely low, or for calcium-hungry crops such as tomatoes, peppers and apples during rapid fruit fill. Return to the standard rate afterwards.
Foliar spray: rapid correction
Delivers calcium directly through the leaf and fruit surface. Apply in early morning or evening. Avoid full sun: the suspension may leave a white residue at higher rates. Filter through 200 micron mesh before use in fine spray nozzles.
Lawn & turf applications
Liquid gypsum delivers calcium and sulphur into the root zone of established turf without digging, disruption, or a change in soil pH in the short term. For lawns sitting on clay that disperses, it is one of the few ways to reach that clay at all.
Lawn: general maintenance
Standard lawn rate for ongoing calcium and sulphur supply. Apply with a watering can fitted with a rose, or through a knapsack sprayer. Water in lightly after application. Calcium is a structural component of grass cell walls. The sulphur deepens green colour and supports protein synthesis in the leaf.
Lawn: clay soil improvement
Higher rate for lawns on clay that disperses, so the surface sits wet and puddles after rain. Dissolving gypsum holds the salt concentration in the surface water above the line at which the clay comes apart, and deeper down calcium swaps onto the clay in place of sodium, without disturbing the lawn surface. This is one of the few ways to get calcium into clay under an established lawn. You cannot dig in amendments without destroying the turf. For best results, combine with hollow-tine aeration in autumn to physically open channels into the clay layer.
Lawn: after aeration or scarifying
Apply immediately after hollow-tine aeration, slit aeration, or scarifying. The open channels and exposed soil allow the liquid gypsum to reach the clay layer beneath the turf. This is the timing that gets it deepest under lawns.
Why liquid gypsum is ideal for lawns
Most soil amendments require digging or incorporation, impossible on an established lawn without destroying it. Liquid gypsum is applied to the surface and washes into the root zone with rain or irrigation. It delivers calcium and sulphur directly where the grass roots are, improves clay structure beneath the turf without disturbance, and does not alter soil pH in the short term. It is one of the very few products that can meaningfully improve the soil under a lawn without lifting the turf.
Single plants
Spot treatment: individual plants
For a single plant you want to feed calcium, apply directly around the root zone at the higher volume. The lawn clay conditioning rate is specified for lawns, so we do not carry it across to borders and beds.
When liquid gypsum will and will not help your drainage
Gypsum is a powerful tool for the right problem, but it is not a universal drainage fix. Before applying, you need to understand what is actually causing your waterlogging. There are three distinct causes of poor drainage, and gypsum only addresses one of them.
Gypsum WILL help: clay that disperses in water
- The clay comes apart in water: the plates separate, block the pores beneath, and the surface seals
- Rain is nearly distilled water, so it dilutes the surface solution towards the concentration below which the clay stops holding together
- Dissolving gypsum puts calcium back into the surface water and holds the concentration above that line, which is why water soaks in instead of standing
- Deeper down, calcium also swaps onto the clay in place of sodium, which lowers the threshold durably. The first effect works on any clay that seals; the second depends on your particular soil
- The RHS advises against watering the garden with artificially softened water in the long term, because softeners replace calcium and magnesium with sodium, and sodium can build up in the soil
- Soils already rich in calcium appear to have least to gain, though that reading rests on two soils and organic carbon is confounded with calcium in the data
Gypsum will NOT help: mechanical compaction
- Soil structure has been physically destroyed by weight: foot traffic, machinery, vehicles on wet ground
- Common on new-build plots, where topsoil is usually stripped before building and construction traffic then compacts the exposed subsoil
- No chemical amendment can undo mechanical compression. The soil needs physical intervention
- The fix is mechanical: deep forking, broadfork aeration, hollow-tine aeration, or double-digging with organic matter
- Once compaction is physically broken, then gypsum can help hold the clay against re-dispersing
Gypsum will NOT help: inadequate physical drainage
- If water has nowhere to drain to, no soil amendment of any kind will fix the problem
- High water table: groundwater sits at or near the surface, especially in winter; the soil may be perfectly structured but is simply saturated from below
- Impermeable subsoil pan: a natural clay or iron pan layer deep in the soil profile blocks all downward water movement regardless of topsoil condition
- Missing land drains: older properties, new-build sites, and gardens on flat terrain may simply lack any drainage infrastructure to carry water away
- Poor site grading: water flows towards, not away from, the problem area due to the lie of the land
- The fix is infrastructure: land drains, French drains, soakaways, regrading, or raised beds to lift the growing zone above the water table
- Applying liquid gypsum (or any other product) to soil that is waterlogged because there is no drainage outlet is a waste of product and money
How to diagnose your drainage problem
01
The screwdriver test: checking for compaction
Push a long screwdriver into moist soil. In our experience, in uncompacted soil it should push in to 15 to 20 cm under moderate hand pressure. If it meets a hard, resistant layer within 5–10 cm, you have a compaction pan. This is a mechanical problem. Gypsum will not fix it. Fork it, broadfork it, or hollow-tine aerate it first.
02
The jar test: checking for dispersed clay
Take a pea-sized crumb of soil from about 10 cm down and air-dry it indoors for a day or two. Half fill a clear jar with rainwater. Tap water carries enough calcium to skew the result. Lower the crumb in without stirring, and look at it after ten minutes, after two hours, and again next morning.
If the crumb falls apart but the water stays clear, that is slaking. Organic matter is the tool for that, not gypsum. If a milky halo spreads from the crumb and hangs in the water, that is dispersion, and gypsum has a job to do.
03
The hole test: checking for a drainage outlet
Dig a hole 30 cm deep and 30 cm wide in the problem area. Fill it with water and time how long it takes to drain. If the water is still sitting in the hole after 24 hours, you have a fundamental drainage problem: either a high water table, an impermeable subsoil pan, or no drainage gradient. This is not a chemistry problem. No liquid product will fix it. You need physical drainage: land drains, a French drain, a soakaway, or raised beds to lift the growing zone above the saturated layer.
04
The ribbon test: confirming clay content
Take a small lump of moist soil and squeeze it between thumb and forefinger to form a flat ribbon. True clay forms a smooth, shiny ribbon 5 cm or longer. If you cannot form a ribbon, your drainage problem is unlikely to be clay-related. Look at subsoil panning, water table, or surface grading instead.
Step-by-step preparation
- Shake the bottle thoroughly. Invert and shake vigorously for 30 seconds. The product is thick and creamy. This is normal for a mineral suspension. Never measure from an unshaken bottle.
- Measure and mix into a small amount of warm water first. Measure the required amount into a small jug or cup containing a splash of warm water. Stir until the thick suspension is fully dispersed. This ensures a thorough mix with no residue left on the spoon or measuring vessel. The warm water dissolves the mineral paste cleanly off everything it touches.
- Add this concentrate to the rest of your water. Pour the pre-mixed concentrate into your watering can or spray container filled with the remaining volume of water. Stir briefly. The suspension will remain stable during normal use.
- Apply to the root zone or foliage. For root drenches, apply evenly around the base and water in. For foliar, filter through fine mesh and apply in early morning or evening.
- Use fresh: do not store diluted. Prepare only as much as you need for each application and use immediately.
Blossom end rot and bitter pit: what we can and cannot say
Blossom end rot is mainly a calcium transport and water-relations problem rather than a shortage of calcium in the soil, so consistent watering matters more than any calcium product. Bitter pit is associated with low calcium in the fruit rather than in the soil, and the evidence for soil-applied calcium is thin. Gypsum is worth using where a soil test shows calcium is genuinely low.
How does liquid gypsum work? The science of calcium and sulphur in soil, lawn and fruit
Start here: what gypsum is and is not for
The science that follows was originally worked out for salt-affected soils in Australia, the Mediterranean and the American west, where irrigation water has carried high levels of sodium into garden soils for decades. UK gardens do not usually have a sodium problem, and that matters. On clay that does not disperse the structural effect is modest, and organic matter does the lasting work. Where clay genuinely disperses and caps, gypsum helps. Gypsum works on clay that comes apart in water, and a crumb of your soil in a jar of rainwater tells you in a day whether yours does: see does liquid gypsum work on clay soil.
Clay is made of flat plates that need something positively charged between them to hold together in crumbs. Calcium does that job well and sodium does it badly. Every clay has a concentration of dissolved salt below which it stops holding together, and rain, being nearly distilled water, dilutes the surface solution towards that line. The top few millimetres disperse, block the pores beneath, and a seal forms. Dissolving gypsum puts calcium back into the surface water and holds the concentration above the line, which is why water soaks in instead of standing. Deeper down, calcium also swaps onto the clay in place of sodium, and that lowers the threshold durably. The first effect works on any clay that seals. The second depends on your particular soil.
The GRDC puts the two routes in that order: "In the short term, the Ca in gypsum increases the ionic strength (the salinity) of the soil solution, which suppresses dispersion... In the long-term, Ca in gypsum replaces Na on soil particles, which helps the soil form aggregates."
No UK survey has measured how much British garden clay disperses. That is exactly why the jar test is the answer: it costs nothing and it tells you about your soil rather than about the average.
Calcium's dual role: soil structure and plant physiology
Calcium is unusual among plant nutrients in that it is simultaneously critical to soil chemistry and plant biology. In the soil, calcium acts as the primary cation binding clay particles together into stable aggregates: the open, crumb structure that allows drainage, aeration, and root exploration. When the salt concentration in the soil water falls below the level a given clay needs, or when sodium takes calcium's place on the exchange sites, the plates separate and the structure collapses into a dense, impermeable layer. Oster and colleagues measured that threshold: calcium-saturated montmorillonite flocculates at 0.25 mol_c m⁻³, and putting sodium on one fifth of the exchange sites raises it to 6.
Inside the plant, calcium is an immobile structural nutrient: unlike nitrogen or potassium, it cannot be remobilised from older tissue to supply new growth. Every new cell wall requires a fresh supply of calcium delivered by the transpiration stream from the roots. When the rate of new cell production in developing fruit exceeds the rate of calcium delivery, typically during rapid fruit expansion in heat or after irregular watering, the newest cells are formed with deficient cell walls that collapse and die. This is the visible result of blossom end rot and bitter pit: not a shortage of calcium in the soil, but a failure of delivery to the fastest-growing tissue.
The calcium role: Cell walls, soil aggregates & fruit integrity
- Structural component of every new plant cell wall via the middle lamella
- Binds clay particles into stable soil aggregates through electrostatic attraction
- Immobile in plants: cannot be translocated from old tissue to new growth
- Deficiency always shows in newest, fastest-growing tissue first
- Critical during fruit set and rapid fruit fill in all fruiting crops
- Delivered as plant-available Ca²⁺ from calcium sulphate dissolution
The sulphate role: sulphur nutrition and the soil solution
- One of the major crop nutrients, supplied here as sulphate
- Required for cysteine, methionine, and other sulphur-containing amino acids
- Dissolving gypsum raises the salt concentration of the soil solution, which suppresses dispersion
- Sodium sulphate formed is soluble and leaches from the root zone with watering
- Fleuridor and colleagues measured gypsum increasing sulphur concentrations in soil and crop tissues within five months of each application
- Immediately available as sulphate-S, with no microbial conversion required
Why does water pool on the surface of clay soils?
When a heavy clay garden floods and stays wet for days, the problem is almost always at the very surface: a hard skin only a millimetre or two thick that water can't get through. The soil below it might be perfectly capable of draining; it just can't be reached. That skin is the surface seal.
Here is how it forms. Clay is made of microscopic flat particles, far too small to see, smaller than a grain of pollen. In a healthy garden these particles stick to each other in small crumbs, and water flows freely between the crumbs through the gaps. When the first heavy rain of the season hits bare clay, raindrops strike with enough force to knock individual particles loose from those crumbs. The loose particles wash into the gaps and clog them. As the surface dries, the trapped particles glue themselves together as a continuous hard crust. The next rain has nowhere to go and pools on top. AHDB describe the first step of it plainly: "The energy of the droplets causes soil particles to detach and block the coarser surface pores."
What decides whether clay particles will stick together properly or fall apart on contact with rainwater is the chemistry sitting on their surfaces. Each clay particle carries a slight negative electrical charge, and just like two negative magnets, two clay particles will push each other apart unless something positively charged is in between to bridge them. Calcium does that bridging job better than anything else that naturally occurs in soil. It has the right charge and the right size to sit tightly between adjacent clay particles and hold them together. Sodium does that job badly, and when it takes calcium's place on the clay surfaces the bridges fail, the particles drift apart, and surface sealing begins. Magnesium is a weaker stabiliser than calcium, not a dispersant.
How liquid gypsum eases and reverses the surface seal: three ways it works
01
The common route: holding the surface together
When gypsum dissolves it releases calcium and sulphate into the soil water. The level of dissolved salt in that water is what decides whether the clay plates drift apart or pull together, and rain, being nearly distilled water, drives it downwards. Dissolving gypsum holds the concentration above the line, which is why water soaks in instead of standing. This route works regardless of what is sitting on the exchange sites. Miller measured it on three non-sodic Georgia soils: surface-applied gypsum held the electrolyte level at 0.5 to 1.3 dS m⁻¹ and cut soil loss by 50% on two of them and 30% on the third. We do not put a clock on it.
02
The second route: calcium onto the exchange
Over a longer period the calcium from the dissolved gypsum swaps onto the clay in place of sodium, and that lowers the concentration at which the clay stops holding together. This is the conditional half of the story: it needs something worth displacing, so on a soil whose exchange sites are already dominated by calcium, adding more calcium changes little. The effect is durable rather than permanent, and it reverses with leaching, sodium input or acidification.
03
Why it needs repeating
Sodium displaced from the clay surfaces combines with sulphate to make a soluble salt that washes down out of the root zone with rainfall. The same solubility that makes gypsum useful is why it does not stay put. Chen and Dick put it plainly: gypsum "may need to be reapplied every couple of years in wet climates or on irrigated fields as the gypsum will leach out of the soil profile". The exchange effect is durable rather than permanent.
Why this works faster than granular gypsum
Standard agricultural gypsum is sold as granules, and a granule dissolves from its outer surface inwards. Milling the mineral fine is what makes it dissolve quickly. Bolan and colleagues measured powdered gypsum dissolving two to ten times faster than pelletised discs, and three to eight times faster again in the presence of soil. We do not put a clock on it, because how fast it reaches your soil depends on your soil and your rainfall. This product is wet-milled down to particles averaging five thousandths of a millimetre across (5 microns) and supplied already mixed into water as a thick suspension, so it is delivered where the seal forms rather than sitting on top of it.
Why UK clay still seals without high sodium
Dispersion. The surface effect does not need sodium. Rain is nearly electrolyte-free, so it dilutes the surface solution towards the concentration below which the clay comes apart, and the top few millimetres seal. Miller measured exactly that on non-sodic soils. Non-sodic does not mean non-dispersive, which is why the jar test matters more than a sodium figure. Ben-Hur and colleagues found surface-applied gypsum decreased soil loss "sharply from the dispersive soils and moderately from the nondispersive soils", so the benefit is graded rather than binary.
Compaction. Walking on wet ground, digging when the soil is too damp, the legacy of building work or trenching: anything that physically crushes the soil's natural crumb structure flat against the surface. The crushed clay at the surface is now exposed raw to every rainfall and disperses on contact, even when the chemistry beneath it is healthy. This is why a trampled lawn or path edge pools water more than an undisturbed border: it has lost its surface structure.
Both produce the same visible problem. Rainwater that should soak in instead sits on the surface for hours or days, then runs off into the lowest corner of the garden. The lawn squelches underfoot. The vegetable bed turns into a shallow pond after every heavy shower. The roots underneath sit in stagnant water with no oxygen.
Gypsum works on the dispersive version, and it is worth being clear about the limit. As Franzen and colleagues put it, "Generally, if soils are not dispersive, gypsum applications do not help water infiltration". Note the word: dispersive, not sodic, and infiltration rather than crusting. The same review records gypsum "effective in reducing soil crusting in laboratory experiments using both sodic and nonsodic soil". Where the surface simply sits wet because the soil is compacted, gypsum does much less, and aeration and organic matter do more.
Five mechanisms of action
01
Cell Wall Construction
Calcium is the primary component of the middle lamella, the layer between plant cells that determines cell wall integrity and firmness. Every rapidly dividing cell in a developing fruit, leaf, or root tip requires a continuous supply of calcium. Liquid gypsum delivers calcium sulphate directly into the root zone in immediately absorbable form, maintaining the rate of calcium supply needed to match fast cell division during fruit set and fill.
02
Clay Flocculation and Soil Structure
Clay particles carry a negative surface charge and need positively charged ions between them to hold together in crumbs. Every clay has a concentration of dissolved salt below which it stops doing so. Dissolving gypsum raises that concentration in the surface water and holds the plates together, which is the common route and does not depend on sodium. Sodium already on the exchange sites raises the concentration the clay needs, and calcium swapping in for it lowers that threshold durably.
03
Calcium onto the Exchange
The RHS advises against watering the garden with artificially softened water in the long term, because softeners replace calcium and magnesium with sodium, and sodium can build up in the soil. Where sodium has built up, calcium from gypsum swaps onto the exchange sites in its place, the sulphate carries the displaced sodium off as a soluble salt, and watering leaches it below the root zone. The effect is durable rather than permanent.
04
Sulphur as Protein Builder
Sulphur is essential for the synthesis of cysteine, methionine, and other sulphur-containing amino acids that are the building blocks of plant proteins, enzymes, and glucosinolates. Gypsum supplies sulphur as sulphate. Fleuridor and colleagues measured gypsum "consistently increased S concentrations (P < .1) in soil and crop tissues as soon as 5 mo after each application" across fourteen Ohio dairy fields. Immediately available as sulphate-sulphur, with no microbial conversion required.
05
Fulvic Acid, the Carrier
The mineral is suspended in fulvic acid, which is the carrier. We hold no trial data on chelation, mobility, membrane permeability or microbial effects, so we make no claim about them.
Scientific References
- Oster, J.D., Shainberg, I. & Wood, J.D. (1980). Flocculation value and gel structure of sodium/calcium montmorillonite and illite suspensions. Soil Science Society of America Journal, 44(5), 955–959.
- Miller, W.P. (1987). Infiltration and soil loss of three gypsum-amended Ultisols under simulated rainfall. Soil Science Society of America Journal, 51(5), 1314–1320.
- Ben-Hur, M. et al. (1992). Phosphogypsum effects on infiltration and erosion of dispersive and nondispersive soils. Soil Science Society of America Journal, 56(5), 1571–1576.
- Grains Research and Development Corporation (2020). Dealing with dispersive soils, western region fact sheet.
- Franzen, D., Rehm, G. & Gerwing, J. (2006). North Dakota State University Extension, SF-1321.
- Bolan, N.S., Syers, J.K. & Sumner, M.E. (1991). Dissolution of various sources of gypsum in aqueous solutions and in soil. Journal of the Science of Food and Agriculture, 57(4), 527–541.
- Chen, L. & Dick, W.A. (2011). Gypsum as an Agricultural Amendment, Bulletin 945. Ohio State University Extension.
- Fleuridor, L. et al. (2021). Gypsum effects on soil health indicators and crop yield. Agronomy Journal, 113(5), 4220–4230.
- Garbowski, T. et al. (2026). Scientific Reports, 16: 21667.
- Kost, D. et al. (2018). Trace element concentrations in soil, crops and water under gypsum amendment. Journal of Environmental Quality, 47(5), 1284–1292.
- Anderson, G.C. et al. (2021). Agronomy, 11(5), 826.
- Lingenfelter, D. & Beegle, D.B. Soil acidity and aglime. Penn State Extension.
- AHDB. Soil capping and slumping.
- Royal Horticultural Society. Clay soils.
- Royal Horticultural Society. Using softened and other types of water.
Liquid gypsum FAQ: what it is, how to apply it, and which questions UK gardeners ask most
Because it is a genuine mineral suspension, not a manufactured liquid. Natural gypsum rock has been wet-milled down to a 5 micron average particle and suspended in water with fulvic acid. Those mineral particles are physically present in the liquid, which is why it is opaque, dense, and settles on standing. Synthetic liquid gypsum products are made from industrial byproduct calcium sulphate processed with chemical dispersants and surfactants. They may appear thinner or more uniform because those synthetic additives prevent natural settling. The thick consistency of this product is what real micronised natural mineral looks like in liquid form, and it settles because there is nothing in it to hold the mineral up, so shake it before use.
Because blossom end rot is a delivery problem, not a supply problem. Calcium is immobile in plants: it travels only upward through the transpiration stream and cannot be moved from old tissue to new. Developing fruit at the blossom end are dividing cells faster than almost anywhere else in the plant. Any disruption to calcium flow, whether hot weather, irregular watering or root damage, causes the newest cells to form with inadequate calcium. Those cells collapse and die. Consistent watering matters more than any calcium product. Gypsum is worth using where a soil test shows calcium is genuinely low.
This product is made from naturally mined gypsum, micronised to a 5 micron average particle and suspended in water with fulvic acid. No synthetic additives, no industrial byproduct gypsum, no chemical dispersants. Most other liquid gypsum products on the market are made from industrial byproduct calcium sulphate, typically FGD gypsum from coal power stations or phosphogypsum from fertiliser manufacture, processed with synthetic surfactants and dispersants to create a pourable liquid. Ours is mined mineral, not an industrial by-product. We make no purity or efficacy claim against by-product gypsum: Kost and colleagues compared mined and FGD gypsum and found most values varied only slightly from 1.00, and much of the field evidence for gypsum on clay was itself run on phosphogypsum. See the Mined vs Synthetic tab for the full comparison.
Lime significantly raises soil pH, which is often undesirable on already-neutral or slightly alkaline soils. Gypsum does not change soil pH. Its neutralising value is zero. Anderson and colleagues measured no self-liming effect in the short term, and gypsum is not a liming material because it cannot neutralise soil acidity. Gypsum also supplies sulphate-sulphur, and on clay that disperses, dissolving gypsum holds the salt concentration of the surface water above the line at which the clay comes apart. If your soil is both acid and calcium deficient, lime corrects both. If your soil is already at the right pH, liquid gypsum is the appropriate calcium source.
Yes, particularly on clay. Calcium is a structural component of grass cell walls, and sulphur supports protein synthesis and deepens green colour. Because it works without digging in, it is one of the few ways to get calcium down to the clay under an established lawn. For lawn maintenance, apply 10 ml per litre at 1 litre per square metre. For lawn clay conditioning, use 15 ml per litre at 1 litre per square metre, fortnightly for three months. Applying immediately after hollow-tine aeration lets it reach the clay layer through the open channels.
Only if the waterlogging is caused by clay that disperses, where the plates come apart in water, block the pores beneath and seal the surface. Gypsum will not fix waterlogging caused by mechanical compaction (foot traffic, machinery), a high water table, an impermeable subsoil pan, missing land drains, or poor site grading. If water sits on your soil because it has nowhere to drain to, no liquid product will fix that. You need physical drainage infrastructure. Use the diagnostic tests in the How to Use tab to identify your specific problem before purchasing.
At standard root drench rates there is no visible residue. Applied as a foliar spray at higher concentrations, the product can leave a fine white mineral deposit on leaves. This is the micronised gypsum itself and is harmless. Apply in early morning so the residue dries and blends in. Any residue washes off with rain or irrigation.
The 1 tsp/L (5 ml/L) rate is the standard maintenance dose. The 2 tsp/L (10 ml/L) rate is the corrective dose for use when deficiency symptoms are already showing or during rapid fruit fill. It delivers twice the calcium per watering. At the rates on the bottle we have not seen leaf scorch. We do not hold trial data on phytotoxicity thresholds, so we do not state one.
Any rapidly fruiting crop with high calcium demand. The most responsive are tomatoes, peppers, aubergines, apples, pears, strawberries, courgettes, cucumbers, and leafy brassicas. Root crops benefit from the sulphur. Lawns benefit from the calcium (cell wall structure) and sulphur (green colour, protein synthesis), and from the calcium reaching the clay beneath the turf. Roses, perennials and container plants take it as a general calcium and sulphur feed.
We do not describe it as organic and we hold no third-party organic certification for it. Two ingredients: mined calcium sulphate, suspended in fulvic acid. No synthetic dispersants. Treat it as you would any garden concentrate. The safety data sheet is the document to read before handling, and we are not able to give a withholding period for edible crops.
Hard water is the calcium and magnesium case, not the sodium one, so hard water on its own is not a reason to use this product. Artificially softened water is the other way round. The RHS advises against watering the garden with artificially softened water in the long term, because softeners replace calcium and magnesium with sodium, and sodium can build up in the soil.
Store in a cool, dry place out of direct sunlight, and above 5°C. Below that, sedimentation may occur, and it is reversible on warming and shaking. Do not allow to freeze. Store in the original container, not pre-diluted. Shake well before each use. Best used within 12 months of purchase, stored as above.
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